Magnetic armature for magnetic arrangements subject to impact stresses

ABSTRACT

A magnetic armature particularly adapted for use with magnet devices which are subject to impact, such as, electro-retaining magnets for knitting machines, includes a magnetic armature head of relatively small mass which is resiliently connected to a magnetic armature body of larger mass. The resilient connection can be provided by a spring or by an intermediate member such as a rubber connector rigidly secured to both the armature head and body.

United States Patent 1191 Hadam MAGNETIC ARMATURE FOR MAGNETICARRANGEMENTS SUBJECT TO IMPACT STRESSES [76] Inventor: Wilhelm Hadam,Bellinostr. H5,

7410 Reutlingen, Germany 22 Filed: Dec.l1, 1972 1211 Appl. No; 313,692

[30] Foreign Application Priority Data 5/1960 Pollakl 335/259 1 June 4,1974 3,564,870 2/1971 Glaunsinger 66/50 R 3.621.422 11/1971 Macy335/267'X 5.7131159 1/1973v Tada 335/259 Primary Eranu'new-George HarrisAttorney, Agent. or Firm-Larson. Taylor & Hinds [5 71 ABSTRACT Amagnetic armature particularly adapted for use with magnet devices whichare subject to impact, such as, electro-retaining magnets for knittingmachines, includes a magnetic armature head of relatively small masswhich is resiliently connected to a magnetic armature body of largermass. The resilient connection can be provided by a spring or by anintermediate member such as a rubber connector rigidly secured to boththe armature head and body.

9 Claims, 5 Drawing Figures PATENTEDJUR 4:914 3.815065 sum lflf I I I IH 151 FIELD OF THE INVENTION The present invention relates to a magneticarmature particularly adapted for use in magnetic apparatus subject toimpact stresses. Thus, for example, the invention is applicable toelectro-retaining magnets of knitting machines, wherein the magnetarmatures are connected to movable members of relatively large mass.

BACKGROUND OF THE INVENTION.

The tractive force of a magnet, that is, the force of the magnetic fieldcreated by a magnet, drops very sharply as the armature is moved fromthe corresponding magnetic core or. magnetic poles. Further, thestrength of the magnetic field which'is required to attract a releasedarmature is a multiple of the force of the magnetic field required tohold or retain an armature in; position. For. this reason, anelectromagnet,

wherever possible, is constructed in the forniofa s6 thereby beseparated or released from the pole surfaces. This can mean that thearmature will be incapable of being subsequently attracted to the polesurfaces because of the inadequate strength of the magnet,notwithstanding the face that the latter is energized. The danger of arelatively heavy armature being irretrievably detached or separated froman energized retaining magnet also exists when the entire magneticapparatus, the actual retaining magnet, or even the armature alone, issubject to impact.

It is also noted that the disadvantage discussed is of increasedseverity in the situation wherein a magnetic armature is arrangedobliquely with respect to the core or pole of a retaining magnet andnon-parallel to the bearing surface thereof, or where the armature ismoved to various distances during mechanical handling so the effect ofseparation from the magnetic core or poles is magnified.

SUMMARY OF THE INVENTION In accordance with the present invention theshortcomings of prior art magnetic armatures discussed above areovercome and an armature provided which is capable of being held with agreater degree of security against release by impact, or accidentalmechanical disturbances, without increasing the power of the magnet.

In its broader aspects, the present invention concerns the provision ofan improved magnetic armature adapted to seat against or engage themagnetic core or pole shoes of a magnet, which armature comprises amagnetic head" of a relatively small mass which is resiliently connectedto a magnetic armature body of a larger mass.

. 2 The resilient connection may be implemented so that the connectionis stressed in one direction only or is stressed in both directions. Inthe latter instance, the

magnetic armature head may be resiliently connected to the armature bodyfor free movement, this, for example, being achieved by an intermediateconnecting layer between the magnetic armature head and the armaturebody which is resiliently deformable under strain or compression.

It is noted that the magnetic armature body need not necessarily be aseparate entity but can, where appropriate, comprise a machine partwhich is magneticallyresponsive and which is of any required form, themachine part being resiliently connected to a corresponding magneticarmature head.

Magnetic armatures constructed in accordance with this invention mayadvantageously be used in various fields including electrical controlsystems for knitting machines in which the armatures of theelectromagnets, and'particularly the electro-retaining magnets, areconnected to movable members of relatively large mass and hence subjectto impact loads. In these instances, such a movable member can, forexample, take the form of a rod or bolt or be provided with a bolt whichis mounted for movement towards a retaining magnet against spring biasand is provided with a resiliently connected armature head adapted to beapplied against the magnet.

It is also noted that tests have confirmed the extraordinaryeffectiveness and impact-resistance of magnetic armatures constructed inaccordance with the present invention.

Other features and advantages of the invention will be set forth in, orapparent from, the detailed description of the preferred embodimentsfound hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified, diagrammatic,side elevational view of a magnetic armature constructed in accordancewith the principles of the invention;

. FIG. 2 is aside elevational view, partially in section, of onepractical embodiment of the improved magnetic armature of the invention;

FIG. 3' is a side elevational view, similar to that of FIG. 2, of asecond practical embodiment of the invention;

FIG. 4 is a fragmentary, part sectional, side elevatio'nal view of aflat knitting machine which incorporates a magnetic armature of the formdepicted in FIG. 2; and

FIG. 5 is a part-sectional view taken along line V V of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, asimplified version of the armature of the invention is shown whichillustrates the principles underlying the invention. As shown, amagnetic armature is broken into a magnetic armature head 10 of a smallmass, denoted m and an armature body 11, of a larger residual mass m,and a spring 12 is used to connect the head 10 and the body 12 together.The face of the armature, denoted 101, is provided on the armature head10 and is applied against a pair of pole shoes denoted l3 and 14.(Alternatively, as discussed above, the armature surface can be appliedagainst the core of an electromagnet.) As mentioned, the braking up ofthe armature into separate, resiliently connected masses providessubstantially improved impact resistance capabilities.

In the practical embodiment illustrated in FIG. 2, the armature body ofthe larger mass m is constituted by a bolt 111 which is movable in thedirections of the double arrow and is provided at its magnet end with apiston 16. A cylinder 17, which is arranged concentrically around thepiston 16 and which is, like piston 16, preferably constructed of alight plastic, includes at one end an inwardly-directed rim 171. Rim 17]engages a shoulder 161 formed on piston 16 and thereby serves anabutment for the piston 16 within the cylinder 17. A hollow'cylindricalshank 102 of an armatureplate 110 is received in thecylinder 17, plate110 corresponding to the armature head 10 of smaller mass shown inFIG. 1. The face 101 of the plate 110 is applied against, or engages, amagnet which generally designated 18 in FIG. 2. Arranged within thecylinder 17 and the concentric cylindrical shank 102 of the magneticplate 110 is a compression spring 112 which bears at one end against thepiston 16 and at the other end against the rear or inner side of theplate 110. I

In the embodiment under consideration, the compression spring 112constitutes the resilient coupling between the bolt 11] (of larger massm and the armature plate 110 (of smaller mass m) and is only effectivefrom the rest position when the bolt 111 moves towards the electromagnet18. The arrangement of the cylinder 17 and the magnetic plate 110 is,however, so constructedthat a limited degree of pivoting thereofrelatively to the longitudinal axis of the bolt 111 can take place sothat the abutment face 101 of the plate 110 is flush against the poleshoes of the electromagnet 18 when the magnetic armature is energized.This construction enables very exact distance and length tolerances tobe achieved and affords a high degree of security against the effects ofimpacts exerted on the bolt Ill, principally in the direction towardsthe electromagnet 18.

In the practical embodiment of the invention illustrated in FIG. 3, amagnetic armature head, in the form of a plate 210, is freely oruniversally movable and is coupled resiliently to a magnetic armaturebody 211 for every direction of movement. This coupling is effected byan intermediate resilient body 212, whichis i preferably constructed ofrubber and which is accordingly in the nature of a rubber spring. Therubber body 212 is rigidly connected by suitable means, such as anadhesive or vulcanization, to both the magnetic annature head 210 andthe armature body 211. Moreover, the rubber body 212 may be stressed intension or compression, the arrangement shown in FIG. 3 affordingprotection against impact in every direction. The magnetic armature head210 is constructed in plate form to enable seating against the poleshoes of the electromagnet 18 and can be connected to the rubber body212 in a preliminary operation to constitute a unitary structure whichis subsequently connected to the magnetic armature body 211. The lattermay be of any desired 4 shape, although in this embodiment, attentionmust be paid to certain longitudinal tolerances of the overall systemduring the mechanical movement of the magnetic armature. 1

Referring to FIGS. 4 and 5, there are shown, in somewhat diagrammaticalform, magnetic armatures of the type illustrated in FIG. 2, togetherwith associated retaining magnets, incorporated in the machine carriageis caused to travel over needle bed 19 in a known manner. A plurality ofelectromagnets 18 are arranged in the mountingplate 21, although. forsimplicity, only two such electromagnets have been illustrated.

The electromagnets 18 are provided with magnetic armatures of a formcorresponding to that illustrated in FIG. 2, and hence include abolt-form magnetic armature body 111 and a magnetic armature plate ofrelatively smaller mass which is resiliently coupled thereto. The bolts111 are each provided with a vertically movable sliding shoe 24 at theend thereof opposite to the corresponding magnet 18. Each of the bolts11] (and its associated shoe 24) is held against the cam bar 20 by meansof a compression spring 25 when the magnet 18 is de-energized. Thecompression springs 25 surround the bolts 111 and are interposed betweenthe underside of the guide plate 22 and the upper ends of the shoes 24.The cam bar 20 produces a continuously repeating presentation of amagnetic armature against its associated electromagnet 18'by causing thearmature plate 110 to move into contact with the pole of that magnet. Inthe embodiment under consideration, the magnet system comprises apermanent magnet with soft iron pole shoes which can be strengthened byelectrical energization through a coil providing a permanent magneticfield and can be weakened by a controllable counteracting field torelease the spring-biased armature. Impacts, which in this case takeplace principally in a direction away from the magnetic armature body111 and towardsthe electromagnet 18, cannot bring about release of themagnetic armature because of the resilient arrangement of the magneticarmature plate.

It will be appreciated by those skilled in the art that although theinvention hasbeen described relative to exemplary embodiments thereof,variations and modifications can be effected in these embodimentswithout departing from the scope and spirit of the invention.

1 I claim:

1. A magnetic armature for magnet devices subject to impact wherein theface of the armature is positioned against the magnetic means of themagnet device which attracts the armature, said armature comprising amagnetic armature head of relatively small mass which lies adjacent tothe magnetic means and abuts the magnetic means upon energization of themagnetic device, a magnetic armature body of a larger mass relativelyremote from themagnetic means and means for resiliently connecting saidarmature head to said armature body.

2. -A magnetic armature as claimed in claim 1 wherein said resilientconnecting means provides free movement of the armature head.

3. A magnetic armature as claimed in claim 2 wherein said resilientconnecting means comprising an intermediate resilient member locatedbetween said armature head and said armature bodyfor rigidly connectingsaid armature head to said armature body, said member being resilientlydeformable under tension and compression.

4. A magnetic armature as claimed in claim 3 wherein said intermediateresilient member is constructed of rubber.

5. A magnetic armature as claimed in claim 1 wherein said magneticarmature comprises a rod-like member including a piston connected to theend thereof towards the magnetic device, said armature further includinga cylinder connected to the armature head into which said pistonprojects and said piston including an abutment for limiting the axialmovement thereof within said cylinder, said resilient means conprising acompression spring located between said piston and said head.

6. A magnetic armature as claimed in claim 5 wherein said piston andsaid cylinder are constructed of a lightweight plastic.

7. A magnetic armature as claimed in claim 6 wherein said cylinderincludes a lip which cooperates with said abutment to limit the axialmovement of the piston.

8. A magnetic armature as claimed in claim 1 in combination with aneedle selection system including electro-retaining magnets, wherein thearmature body is associated with a bolt-like movable member ofrelatively high mass which is mounted for movement against spring forcestowards a corresponding electro-retaining magnet, said armature headbeing adapted to abut said magnet.

9. A magnetic armature as claimed in claim 1 in combination with needleselection system, including electro-retaining magnets, wherein the saidarmature body comprises a movable bolt member, said system includingmeans for mounting said bolt member for movement towards a correspondingretaining magnet, said spring means for opposing the movement of saidbolt member, said armature head being resiliently held in abutmentagainst said magnet.

1. A magnetic armature for magnet devices subject to impact wherein the face of the armature is positioned against the magnetic means of the magnet device which attracts the armature, said armature comprising a magnetic armature head of relatively small mass which lies adjacent to the magnetic means and abuts the magnetic means upon energization of the magnetic device, a magnetic armature body of a larger mass relatively remote from the magnetic means and means for resiliently connecting said armature head to said armature body.
 2. A magnetic armature as claimed in claim 1 wherein said resilient connecting means provides free movement of the armature head.
 3. A magnetic armature as claimed in claim 2 wherein said resilient connecting means comprising an intermediate resilient member located between said armature head and said armature body for rigidly connecting said armature head to said armature body, said member being resiliently deformable under tension and compression.
 4. A magnetic armature as claimed in claim 3 wherein said intermediate resilient member is constructed of rubber.
 5. A magnetic armature as claimed in claim 1 wherein said magnetic armature comprises a rod-like member including a piston connected to the end thereof towards the magnetic device, said armature further including a cylinder connected to the armature head into which said piston projects and said piston including an abutment for limiting the axial movement thereof within said cylinder, said resilient means conprising a compression spring located between said piston and said head.
 6. A magnetic armature as claimed in claim 5 wherein said piston and said cylinder are constructed of a lightweight plastic.
 7. A magnetic armature as claimed in claim 6 wherein said cylinder includes a lip which cooperates with said abutment to limit the axial movement of the piston.
 8. A magnetic armature as claimed in claim 1 in combination with a needle selection system including electro-retaining magnets, wherein the armature body is associated with a bolt-like movable member of relatively high mass which is mounted for movement against spring forces towards a corresponding electro-retaining magnet, said armature head being adapted to abut said magnet.
 9. A magnetic armature as claimed in claim 1 in combination with needle selection system, including electro-retaining magnets, wherein the said armature body comprises a movable bolt member, said system including means for mounting said bolt member for movement towards a corresponding retaining magnet, said spring means for opposing the movement of said bolt member, said armature head being resiliently held in abutment against said magnet. 